The Best Medicine: The Complete Health and Preventive Medicine Handbook by Kurt Butler and Lynn Rayner MD (Harper & Row: $32.95).

With the growth of health maintenance into big business, exercise experts, nutrition gurus and purveyors of food supplements often make contradictory claims on our value systems and our pocketbooks.

To clarify a confusing subject, “The Best Medicine,” published earlier this year, turns out to be the least medicine. Kurt Butler, a medical columnist, and physician Lynn Rayner hark back to a simpler time of common-sense dietary and exercise practices, showing why certain trends are extreme, faddish or gimmicky.

Choosing foods listed under the familiar Recommended Daily Allowance, they maintain, “in most cases, ensures adequate nutrition.” Vitamins are recommended only if one is medically at risk, and megadoses of vitamins A and C, particularly among diabetics, can prove harmful.

In their brisk overview of sports medicine and prevention of common injuries, the authors, keeping matters simple, describe calisthenics that can be performed at home in the “poor person’s gym.” They list the pros and cons of the most popular forms of exercise, including a chart illustrating the number of calories burned. (Cross-country skiing comes in first at 600 to 1,100 per hour.)

As for the most popular slim-down methods of the last 20 years, the claims of diet books that have swept the nation are compared and short shrift made of most. Several prudent diets are recommended, and dieters are warned not to subsist on fewer than 1,000 calories per day without medical supervision.

Butler and Rayner have divided an immense amount of material into seven basic sections to be read in any order. From sex and reproduction to treating common illnesses at home to eye-opener chapters on alternative health methods (acupuncture, iridology, Yoga) to common sports injuries and the use of drugs in sports, there’s unlikely to be any question left unanswered in this mini-encyclopedia.